Method For Producing A Three-Dimensional Component

ABSTRACT

The invention relates to a method for producing a three-dimensional component by an electron-beam, laser-sintering or laser-melting process, in which the component is created by successively solidifying predetermined portions of individual layers of building material that can be solidified by being exposed to the effect of an electron-beam or laser-beam source (2) by melting on the building material, wherein thermographic data records are recorded during the production of the layers, respectively characterizing a temperature profile of at least certain portions of the respective layer, and the irradiation of the layers takes place by means of an electron beam or laser beam (3), which is controlled on the basis of the recorded thermographic data records in such a way that a largely homogeneous temperature profile is produced, wherein, to irradiate an upper layer, a focal point (4) of the electron beam or laser beam (3) is guided along a scanning path (17), which is chosen on the basis of the data record characterizing the temperature profile of at least certain portions of the layer lying directly thereunder or on the basis of the data records characterizing the temperature profiles of at least certain portions of the layers lying thereunder.

The invention relates to a method for producing a three-dimensionalcomponent by way of an electron beam, laser sintering or laser meltingmethod, in which the component is created by successively solidifyingpredetermined sections of individual layers of building materialsolidifiable by the action of an electron or laser radiation by way offusion of the building material, having the further features of thepreamble of claim 1.

Moreover, the invention relates to an apparatus for selective laserpowder processing, embodied to carry out the method for producing thethree-dimensional component.

The prior art has disclosed methods which are usually referred to aslaser sintering or laser melting methods. In such methods, layers madeof building material are applied, said layers being heated locally bythe action of radiation, in particular electron or laser radiation, tosolidify at the points corresponding to the cross section of the objectto be produced. Here, there may be a connection to a layer lyingtherebelow. For irradiation purposes, a focal point of the laser beam istypically guided along a scanning path selected in such a way that thecross section of the object to be produced is completely covered.

Correspondingly, apparatuses for selective laser powder processingembodied thus have a building platform for receiving a powder bed madeof solidifiable building material, a powder coating system for applyinga powder layer onto the building platform, a laser radiation source forproviding the focused laser beam, a scanning device for guiding thefocused laser beam along the scanning path and a control device. Thecontrol device is embodied to control the laser radiation source in amanner dependent on building data characterizing the three-dimensionalform of the object to be produced; it comprises electronic storage mediawhich interact with a scanner for deflecting the laser beam.

Although such electron beam melting or sintering methods or lasermelting or laser sintering methods were found to be efficient means forproducing components, it was found to be disadvantageous when largetemperature gradients in the layer to be solidified during theproduction of the object are generated. Such high temperature gradientscan lead to the generation of cracks in the produced material and, ingeneral, adversely affect the quality of the produced object. Moreover,local overheating may occur, leading to the local melting bed generatedby the laser beam assuming larger dimensions than originally envisaged.This adversely affects the accuracy of the production method or leads tomaterial unevennesses such as burrs and the like being created, whichneed to be removed with much outlay after the production of the object.

Therefore, it is advantageous if the action of temperature caused by thelaser beam is as uniform as possible during the production of thethree-dimensional object. To this end, US 2004/0200816A1 proposes theprovision of at least one thermographic detector for acquiring datarecords which characterize, at least in sections, the temperatureprofiles of layers consisting of solidified building material. In orderto equalize the occurring temperature gradients, a heating device iscontrolled appropriately or process parameters of the laser, inparticular the scanning speed and/or the laser power are adapted, inorder to control the temperatures over the coater plane.

Proceeding from this prior art, it is an object of the present inventionto specify a method in which local overheating of the applied buildingmaterial is avoided and temperature gradients occurring during theproduction are minimized. Furthermore, it is an object of the inventionto specify an apparatus suitable for efficiently carrying out thismethod.

The object is achieved by a method of the type set forth at the outsethaving the characteristic features of patent claim 1. In respect of theapparatus, the object is achieved by an apparatus for selective laserprocessing, which is embodied to carry out the method according to theinvention.

In a method for producing a three-dimensional component by way of anelectron beam, laser sintering or laser melting method, at least onedata record is generated, which characterizes at least partially thetemperature profile of at least on layer directly below the upper layerto be irradiated. As an alternative or in addition thereto, data recordsare generated which characterize, at least in sections, the temperatureprofiles of the layers lying below the upper layer. A thermographicacquisition of the irradiation plane is provided for generating the datarecords. During the irradiation of the upper layer, a focal point of thelaser beam is guided along a scanning path, selected in a mannerdependent on the data record or records acquired thermographically, forthe purposes of generating a largely homogeneous temperature profile. Inparticular, provision is made during the irradiation of the upper layerfor regions which have a high temperature due to preceding radiationaction to be omitted initially and for the irradiation process to becontinued at different points.

In more complex cases, the thermographic acquisition identifies regionsin which elevated temperatures prevail, in particular higher temperaturein comparison with the temperatures prevailing in the surroundingregions. Thus, these are local temperature maxima which are acquired.The scanning path is selected in such a way that these surroundingregions are initially irradiated such that there can be an equalizationof the temperature gradient. At the same time, there is dissipation ofheat in the hot region, for example by heat transfer to the surroundingsby way of convection. As a result, the temperature gradient prevailingbetween the regions is equalized and the region previously too hot canbe irradiated after the irradiation of the surrounding regions iscompleted, without there being a risk of overheating, in the case ofwhich a melting zone that is too large could be created.

Preferably, the irradiation of the upper layer is controlled in such away that an energy influx per unit area imparted by the laser beam ontothe upper layer of the applied powdery construction material is adaptedin a manner dependent on the data record or records which characterize,at least in sections, the temperature profiles of the layers lying underthe upper layer. Thus, in addition to adapting the scanning path to theacquired temperature profile or profiles, provision is made for anadaptation of process parameters modifying the energy influx per unitarea to be undertaken in order to further counteract excessive localheating.

Process parameters which are modified to adapt the energy influx perunit area preferably comprise a scanning speed of the laser beam, a sizeof the focal point, a laser pulse frequency, a laser pulse durationand/or a laser power.

Therefore, in accordance with alternative embodiments, provision is madefor the irradiation of the layers to be undertaken by means of pulsed orcontinuous laser irradiation. It is understood that the correspondingapparatuses are embodied in such a way that these process parameters arecorrespondingly modifiable. Thus, in particular, the laser pulsefrequency, the laser pulse duration and/or the laser power of a laserradiation source embodied to provide the laser beam is/are regulable. Ascanning device embodied to deflect the laser beam and guide the focalpoint over the regions of the upper layer to be irradiated accordinglyhas an optical unit suitable for adapting the size of the focal point.

In a preferred refinement, the start of the irradiation of a section ofthe upper layer is delayed by a predetermined or predeterminable timeinterval selected in a manner dependent on the data recordcharacterizing, at least in sections, the temperature profile of thelayer lying immediately therebelow or in a manner dependent on the datarecords characterizing, at least in sections, the temperature profilesof the layers lying therebelow. Therefore, if the thermographicacquisition identifies regions with a high temperature or areas withhigh temperature gradients, an irradiation of the upper layer in theseregions is initially postponed. Here, provision is made for the durationof the time interval delaying the irradiation to be selected in a mannerdependent on an acquired maximum temperature or in a manner dependent ona maximum temperature gradient in order to achieve the best possibleadaptation of the temperatures.

Accordingly, provision is made in a development of the invention for theirradiation of the section of the upper layer to be delayed until thetemperature of the section of the upper layer, which is decisivelydetermined by the temperature profiles of the layer or layers arrangedtherebelow, has sunk below a predeterminable threshold. Such a method isperformable in a completely automated manner by means of anappropriately configured control device with logic circuits, processorsor the like. The thermographic data records are preferably acquired atthe same time with the production process such that the irradiationprocess of the section can be initiated as soon as the temperature hassunk below the predeterminable threshold.

The at least one temperature profile is acquired by means of athermographic detector, which is therefore arranged by a buildingchamber having a building platform and acquires, at least in sections,the irradiation plane.

In a preferred exemplary embodiment, the temperature profile of the datarecord characterizing the respective layer is acquiredsection-by-section by means of a movably mounted thermographic detectorwhich is movable over the entire irradiation area. Like a scanning headof a scanning device, the thermographic detector is movableindependently of the alignment of the scanning apparatus of the laserbeam such that, where necessary, it is also possible to acquire regionsof the upper layer lying away from the surroundings around the focalpoint. Due to the time that has already elapsed since the irradiation,these regions have generally cooled down further, which may beimportant, in particular, for the selection of the initial point of thescanning path for irradiating the next layer.

In an alternative preferred exemplary embodiment, the temperatureprofile of the data record characterizing the respective layer isacquired by means of a stationary thermographic detector, which isarranged over the irradiation area and acquires the latter in theentirety thereof. A thermographic sensor embodied thus therefore allowsthe acquisition of the points corresponding to the cross section of theobject to be produced in the entirety thereof. Hence, the data recordsacquired thus contain a thermographic snapshot of the upper layer whichis taken into account for the purposes of optimizing the scanning pathin respect of the generation of a homogeneous temperature profile.

Preferably, the thermographic data records, which are acquired by themovable or stationary thermographic detector, comprise image data whichare output by way of a display unit, in particular during the generativeproduction of the three-dimensional object. Therefore, the operatingstaff have available all the thermographic information to them, and sothere can be a manual intervention into the production process wherenecessary. The different acquired temperatures can be output by way ofsuitable color coding.

Provision is made for the data record characterizing the temperatureprofile of the respective layer to be acquired when irradiating therespective layer. Accordingly, the thermographic acquisition is carriedout simultaneously with the irradiation process in order to minimize thetime outlay.

In an alternative exemplary embodiment, provision is made for the datarecord characterizing the temperature profile of the respective layer tobe acquired after the respective layer was irradiated and after a powderlayer of non-solidified building material was applied thereabove, fromwhich powder layer the following layer of the component is intended tobe formed in a further method step. This is advantageous in that thethermographic acquisition contains a dissipation of heat into the layerconsisting of powder material arranged thereabove. Accordingly, it ispossible for a predetermined time interval after the application of thenew upper powder layer to be predeterminable, only after which therecording of the thermographic measurement data is started. As a resultof this, sufficient time for dissipating the heat is available.

The previous explanations are directed to specifying a method by meansof which the building process of an individual component can beoptimized. However, generative building methods such as electron beam orlaser sintering or laser melting are increasingly also used for massproduction. Preferably, provision can therefore be made for thethermographic data records of at least one component to be stored in astorage device and for at least one of the thermographic data records tobe used to control the irradiation of a layer of a componentmanufactured later in time. Thus, the knowledge from a precedingbuilding process is used to improve the next building process. This isof interest, in particular, in the case of identical or at least partlyidentical components.

In so doing, those thermographic data records which, within the scope ofthe building process, correspond to the irradiated layer or a subsequentlayer are preferably taken into account when irradiating a layer. Whatthis means is that when e.g. the second layer of a component isirradiated, the thermographic data records of the second and/or thethird layer of one or more previously manufactured components are takeninto account. Taking into account the identical layer number bringsabout an acceleration in the calculation or an acceleratedpredetermination of the scanning path since local temperature maxima arealready considered to be known. Scanning paths can therefore becalculated in advance in a layer-dependent manner. By contrast, takinginto account at least one subsequent layer, i.e., for example, the thirdlayer, allows the anticipatory avoidance of too strong temperaturegradients in the subsequent layer.

The components manufactured in advance could have been manufacturedsimultaneously and/or in succession. When taking into account thethermographic data records of components manufactured at the same time,averaging of the temperature information of the individual data recordscan be undertaken in order to average out statistical variations. Bytaking into account the thermographic data records of componentsmanufactured in succession, an improvement of the scanning path can beachieved to the extent that a successive improvement of the scanningpath is adapted. That is to say, the thermographic data records of acomponent manufactured first are initially used for improving thescanning paths of the next, i.e. the second, component. Equally, thethermographic data records of the second component are used to improve,i.e. avoid temperature gradients and/or local temperature peaks, a thirdcomponent. Instead of running through this adaptation or improvement upto e.g. the tenth component, it is also possible to take into accountthe thermographic data records of a plurality of components manufacturedsuccessively, e.g. the first, second and third component. In a purelyexemplary manner, this can be carried out by a time series-assistedanalysis of the thermographic data records.

Particularly advantageously, the thermographic data records of aplurality of components manufactured simultaneously can be taken intoaccount and these can be taken into account in a successive manner. As aresult, the adaptation of the scanning path can be further optimizedwhile avoiding statistical deviations.

An apparatus for selective laser powder processing, embodied to carryout the method according to the invention, comprises a preferably heightadjustable building platform for receiving a powder bed made ofsolidifiable building material, a powder coating system for applying apowder layer onto the building platform, the laser radiation source forproviding the focused laser beam which is incident on the powder layerfor selectively solidifying the building material, the scanning devicefor guiding the focused laser beam along the scanning path, the—movablymounted or stationary—thermographic detector for acquiring the datarecords which characterize, at least in sections, the temperatureprofiles of layers consisting of solidified building material, and acontrol device for controlling the laser radiation source in a mannerdependent on the acquired data records.

The data records can be stored in a storage device which has such anoperational connection to the control device and the scanning devicethat the scanning path for producing the upper layer is controllable ina manner dependent on the data record which characterizes, at least insections, the temperature profile of the layer lying directly below theupper layer to be irradiated or the scanning path is controllable in amanner dependent on the data records which characterize, at least insections, the temperature profiles of the layers lying below the upperlayer to be irradiated. An apparatus embodied thus enables efficientimplementation of the method according to the invention, and so aproduction of high-quality objects or components is made possible.

In a preferred exemplary embodiment of the invention, a movably mounteddetector is provided for acquiring the data record characterizing thetemperature profile of the respective layer, which detector is movablein the style of a scanning head over the whole irradiation area in amanner independent of the movement of the scanning device. This enablesthe selective acquisition of regions of the irradiation plane which lieaway from the immediate surroundings of the focal point.

Any sensors designed for acquisition of infrared radiation, such as, inparticular, semiconductor sensors, thermal imaging cameras or the like,can be provided as thermographic detectors.

Below, the invention will be explained in more detail on the basis ofspecific exemplary embodiments, which are depicted in the figures of thedrawing. In detail:

FIG. 1 shows a schematic design of an apparatus for selective laserpowder processing in accordance with a first exemplary embodiment of theinvention,

FIG. 2 shows a schematic design of an apparatus for selective laserpowder processing in accordance with a second exemplary embodiment ofthe invention, and

FIG. 3 shows a plan view of an irradiation plane, wherein a scanningpath of a laser beam is selected in a manner dependent on data recordswhich characterize the temperature profiles of layers lying below theirradiation plane.

Parts corresponding to one another have been provided with the samereference sign in all figures of the drawing.

FIG. 1 shows an apparatus for selective laser powder processing,embodied to control an irradiation process in a manner dependent onthermographically acquired data. The apparatus 1 comprises a laserradiation source 2 for providing a laser beam 3. For the purposes ofguiding a focal point 4 of the laser beam 3 over an irradiation plane 5,a scanning device 6 is equipped with a corresponding optics, such as, inparticular, lenses, mirrors or the like. Powder layers made of buildingmaterial which are solidifiable by the action of the laser beam 3 arearrangeable in a building chamber 7, which is bounded below by aheight-adjustable building platform 8.

A powder coating system 9 which has a metering container for receivingbuilding material and coating means for the uniform distribution ofbuilding material, such as doctor blades, rollers or the like, isprovided for the layer-by-layer application of building material intothe building chamber 7 or onto the building platform 8.

The apparatus 1 moreover has a storage apparatus 10, in which buildingdata characterizing the three-dimensional form of the object to beproduced or of the component to be produced are stored.

The scanning device 6 and the laser radiation source 3 are connected tothe storage device 10 by way of a control device 11 such that processparameters of the laser beam source 2, and hence the scanning path ofthe laser beam 3 in accordance with the building data characterizing theobject, are controllable.

A thermographic detector 12 is arranged over the irradiation plane 5 forthe purposes of acquiring temperature profiles of irradiated layers. Byway of the control device 11, the thermographic detector 12 is connectedto the storage device 10 such that data records which characterize thetemperature profiles of irradiated layers can be stored in the storagedevice for subsequent evaluation by the control device. The data recordsacquired by the thermographic detector 12 comprise image data which aredisplayable by means of a display unit 13 which, for example, comprisesan LC (liquid crystal) display.

In the exemplary embodiment shown in FIG. 1, the thermographic detector12 has a stationary arrangement and it is equipped with an acquisitionregion 14 which contains the entire irradiation plane 5. Thethermographic detector 12, the storage device 10, the control device 11,the scanning device 6 and the laser radiation source 2 have such anoperational connection that the scanning path of the laser beam 3 andfurther process parameters such as, in particular, the scanning speed ofthe laser beam, the size of the focal point, the laser pulse frequency,the laser pulse duration and/or the laser power are controllable in amanner dependent on the acquired temperature profiles.

FIG. 2 shows a schematic design of a second exemplary embodiment of theinvention. Here, essential components correspond to the parts alreadydescribed in relation to FIG. 1, and so only the differences arediscussed below.

In contrast to the first exemplary embodiment, the thermographicdetector 12 is movably mounted and displaceable over the entireirradiation plane 5 in the style of a scanning head. At a given instant,the acquisition region 14 of the detector 12 only covers part of theirradiation plane 5. The thermographic detector 12 is movableindependently of the scanning device 6, and so it is also possible toacquire regions of the irradiation plane 5 which are situated away fromthe immediate surroundings of the focal point 4.

In a method for producing the three-dimensional component or thethree-dimensional object by way of the laser melting method there is alayer-by-layer application of powdery building material and alayer-by-layer solidification of the building material at the pointscorresponding to the cross section of the component. After completing anirradiation process, the building platform 8 is lowered in order toenable an application of the next layer of non-solidified buildingmaterial.

Provision is made for thermographic data records to be acquired by meansof the detector 12, which thermographic data records characterize thetemperature profiles of the just irradiated layer, possibly taking intoaccount all temperature profiles of the layers arranged therebelow. Inaccordance with alternative embodiments, these data records are acquiredsimultaneously with an irradiation process occurring in the buildingchamber 7 or they are acquired at an instant after a layer wasirradiated and a layer made of non-solidified building material, lyingthereabove, was already applied. On the basis of the thermographic datarecords, the irradiation of the upper layer is controlled in such a waythat the scanning path of the laser beam 3 is selected in a mannerdependent on the temperature profiles characterizing the layer or layerslying under the upper layer. In particular, provision is made for thescanning path to be guided in such a way that hot regions are irradiatedat a later stage in order to enable an intermediate equalization of thetemperature gradients. This should avoid excessive regional heating.

In order to generate largely homogeneous temperature profiles, provisionis made for further process parameters to be adapted in a mannercorresponding to the acquired thermographic data records. Thus, anenergy influx per unit area imparted by the laser beam may be reduced inregions of high temperature by virtue of the scanning speed of the laserbeam, the size of the focal point, the laser pulse frequency, the laserpulse duration and/or the laser power being modified accordingly.

During the production process the image data contained in thethermographic data records are output by way of the display unit 13 suchthat manual intervention by operating staff is made possible wherenecessary. However, the method for generating largely homogeneoustemperature profiles is suitable for being carried out fullyautomatically, for the purposes of which the control device 11 isequipped with corresponding evaluation electronics.

In addition to adapting process parameters and the scanning path,provision is made for the start of the irradiation of a section of theupper layer to be delayed in the case of a possibly too high regionalaction of heat. If regions of high temperature are registered during thethermographic acquisition, an irradiation of the upper layer is delayeduntil the temperature has sunk below a predeterminable threshold.

FIG. 3 schematically shows the irradiation plane 5 with an applied layermade of non-solidified building material 7 in a plan view. A contour 15corresponds to the outline of a cross section of the component to beproduced. Furthermore, a region 16 is depicted in a hatched manner inFIG. 3, said region corresponding to a region of increased temperatureregistered by the detector 12. In order to avoid too strong local fusionof the powdery building material 7, the scanning path 17 is selected insuch a way that the region 16 is initially omitted. Proceeding from theinitial point 18, the laser beam is initially guided along the contour15 until the focal point of the laser beam 3 returns to the initialpoint 18. Then, the focus is guided along the zigzag-shaped scanningpath 17 shown in FIG. 3 until the cross-sectional area of the object tobe produced was completely covered with the exception of the region 16.Only then is the region 16, which has cooled down in the meantime,irradiated in a manner not depicted in any more detail.

It is understood that it is not necessary for a continuous path as shownin FIG. 3 to be described by the scanning path 17. Thus, for example, itis also possible to irradiate in succession regions of the irradiationplane 5 which are arranged in a manner separated in space from oneanother.

Furthermore, combinations of the shown exemplary embodiments arepossible and envisaged within the scope of the present invention. Inparticular, it is possible to arrange a plurality of—stationary ormovably mounted—thermographic detectors 12 for the purposes of acquiringthe thermographic data records.

LIST OF REFERENCE SIGNS

-   1 Apparatus-   2 Laser radiation source-   3 Laser beam-   4 Focal point-   5 Irradiation plane-   6 Scanning device-   7 Building chamber-   8 Building platform-   9 Powder coating system-   10 Storage device-   11 Control device-   12 Thermographic detector-   13 Display unit-   14 Acquisition region-   15 Contour-   16 Region-   17 Scanning path-   18 Initial point

1-15. (canceled)
 16. A method for producing a three-dimensionalcomponent, the method comprising: receiving, with a building platform, apowder bed comprising solidifiable building material; applying, with apowder coating system, a powder layer onto the building platform;focusing, with a laser radiation source, a laser beam incident upon thepowder layer; guiding, with a scanning device, the laser beam to thepowder layer, thereby selectively solidifying the building material;acquiring, with a thermographic detector, temperature data comprising atemperature profile of one or more layers of building material, the oneor more layers comprising solidified building material; storing, with amemory of a control device, the temperature data; controlling, with aprocessor of the control device, the laser radiation source based atleast in part on the temperature data; determining, based at least inpart on the temperature data, a region of local overheating within alayer of building material in comparison to a surrounding region,wherein a next powder layer situated directly above the layer ofbuilding material includes at least one portion of the next powder layerwithin the region of local overheating; and modifying, with the controldevice, at least one process parameter adapting the energy influx perunit area based on the temperature data.
 17. The method of claim 16,wherein the thermographic detector comprises a movably mountedthermographic detector, the movably mounted thermographic detector beingmovable independently of the scanning device.
 18. The method of claim17, wherein the movably mounted thermographic detector is configured asa scanning head, movable over at least a portion of an irradiation area.19. The method of claim 17, wherein the temperature data is acquiredsection-by-section while the movably mounted thermographic detectormoves over at least a portion of an irradiation area.
 20. The method ofclaim 16, wherein the modifying, with the control device, the at leastone process parameter adapting the energy influx per unit area is basedat least in part on the temperature data.
 21. The method of claim 20,wherein the modifying, with the control device, the at least one processparameter adapting the energy influx per unit area comprises modifying ascanning speed of the laser radiation source, a size of a focal point ofthe laser radiation source, a laser pulse frequency of the laserradiation source, a pulse duration of the laser radiation source, and/oran output power of the laser radiation source.
 22. The method of claim16, further comprising delaying, with the control unit, irradiation ofat least part of the next powder layer until determining, based at leastin part on the temperature data, that the region of local overheatinghas cooled below a temperature threshold.
 23. The method of claim 22,further comprising: delaying, with the control unit, irradiation of theentirety of next powder layer until determining, based at least in parton the temperature data, that the region of local overheating has cooledbelow a temperature threshold.
 24. The method of claim 16, wherein thethermographic detector comprises a stationary thermographic detectorhaving an acquisition region comprising an entirety of an areairradiated by the laser radiation source.
 25. The method of claim 16,wherein the thermographic detector is configured to acquire temperaturedata comprising a temperature profile corresponding to a first layer ofbuilding material after the laser radiation source has irradiated thefirst layer of building material.
 26. The method of claim 25, whereinthe thermographic detector is configured to acquire temperature datacomprising the temperature profile corresponding to the first layer ofbuilding material after the next powder layer has been applied over thefirst layer of building material.
 27. The method of claim 16, furthercomprising: controlling based at least in part on the temperature data,with the control unit, irradiation of a layer of a componentmanufactured later in time.
 28. The method of claim 27, furthercomprising: controlling, based at least in part on the temperature data,with the control unit, the irradiation of the layer of the componentmanufactured later in time, wherein the temperature data corresponds toat least two components manufactured earlier in time.
 29. The method ofclaim 28, wherein the at least two components are manufacturedsimultaneously or in succession.
 30. The method of claim 16, furthercomprising: determining, based at least in part on the temperature data,a scanning path for irradiating the next powder layer so as to initiallyirradiate the surrounding region with the radiation source prior toirradiating the at least one portion of the next powder layer within theregion of local overheating; and controlling the laser radiation sourceso as to irradiate the next powder layer according to the scanning path.31. The method of claim 30, further comprising: imparting a delay, withthe control unit, for controlling the laser radiation source so as toirradiate the next powder layer according to the scanning path, whereinthe delay comprises a time interval selected based at least in part on aportion of the temperature data, the portion of the temperature datacorresponding to a layer of building material situated immediately belowthe next powder layer.
 32. The method of claim 16, wherein the at leastone process parameter comprises a laser pulse frequency.
 33. The methodof claim 16, wherein the at least one process parameter comprises alaser pulse duration.
 34. The method of claim 16, wherein the at leastone process parameter comprises a focal point of the laser beam.
 35. Themethod of claim 16, further comprising: controlling, with the controldevice, the laser radiation source so as to irradiate the next powderlayer according to the scanning path modifying, with the control unit, ascan path so as to irradiate a portion of the region of localoverheating before and after at least one portion of the surroundingregion.